System and method for operating a heat pump

ABSTRACT

Methods and system for operating a heat pump in different operating modes and providing a predictable heat pump response when the heat pump is transitioned between the different operating modes are presented. In one example, a controller that includes executable instructions for providing a bumpless compressor command for operating the heat pump is disclosed.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 14/531,580, entitled “SYSTEM AND METHOD FOR OPERATING A HEAT PUMP,”filed on Nov. 3, 2014. The entire contents of the above-referencedapplication are hereby incorporated by reference in its entirety for allpurposes.

FIELD

The present description relates to methods and a system for controllingoperation of a heat pump of a vehicle. The methods and system may beparticularly useful for heat pumps that are operated to heat and cool avehicle's passenger cabin.

BACKGROUND AND SUMMARY

A heat pump may be configured to heat a vehicle's passenger cabin at lowambient temperatures and cool the vehicle's passenger cabin at higherambient temperatures. The heat pump may transition from a heating modeto a cooling mode in response to driver input, or in response toautomated controller commands that are based on ambient and/or passengercabin environmental conditions. The heat pump may be transitionedbetween heating and cooling modes by changing a path that refrigerantflows within the heat pump. Additionally, the heat pump may becontrolled responsive to different inputs during different operatingmodes. As a result, it may be possible for heat pump control signals tochange significantly when the heat pump is switched from operating in aheating mode to operating in a cooling mode, or vice-versa. The changein heat pump control signals may be objectionable to vehicle occupantsor it may increase degradation of heat pump components. Therefore, itmay be desirable to provide a system and method that allows a heat pumpto transitions between operating modes in a seamless way.

The inventors herein have recognized the above-mentioned disadvantagesand have developed a heat pump method, comprising: commanding acompressor to provide a desired evaporator temperature in response tooutput of an evaporator temperature controller and output of arefrigerant pressure controller in a first heat pump operating mode; andcommanding the compressor to provide a desired heater core temperaturein response to output of a heater core temperature controller and outputof the refrigerant pressure controller in a second heat pump operatingmode.

By combining outputs of two controllers in one mode and two differentcontrollers in a second mode, it may be possible to provide thetechnical result of providing a bumpless or seamless change in heat pumpoperation during a heat pump mode change. In one example, output of twocontrollers is adjusted based on output of at least one differentcontroller so that controllers outputting commands for a control modebeing entered are adjusted to command values that maintain a compressorcommand before and after the heat pump changes operating modes. In thisway, a sum of output of controllers providing output for a new heat pumpoperating mode may match or equal a sum of output of controllerssupplying commands for a different heat pump operating mode so that aheat pump compressor speed is not substantially changed during atransition or change from one heat pump mode to a next heat pump mode.

The present description may provide several advantages. Specifically,the approach may improve heat pump mode transitions. Additionally, theapproach may improve heat pump durability. Further, the approach mayreduce objectionable noise of a vehicle that includes a heat pump.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an embodiment, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings, where:

FIG. 1 is a schematic diagram of a vehicle;

FIG. 2 shows an example vehicle climate control system for the vehicleof FIG. 1;

FIG. 3 shows an example vehicle driveline for the vehicle of FIG. 1;

FIG. 4 shows an example controller block diagram for a heat pump;

FIG. 5 shows an example simulated sequence for operating a vehicle heatpump system according to the method of FIG. 6; and

FIG. 6 shows a method for operating a heat pump system.

DETAILED DESCRIPTION

The present description is related to operating a heat pump of a vehicleand transitioning the heat pump between its different operating modes.The vehicle may be a passenger vehicle as is shown in FIG. 1 or acommercial vehicle (not shown). The vehicle includes a climate controlsystem including a heat pump as is shown in FIG. 2. The climate controlsystem may include an engine that is part of a hybrid powertrain as isshown in FIG. 3. The heat pump may be operated by a controller as isshown in the block diagram of FIG. 4. The heat pump may transitionbetween heating and cooling modes or vice-versa as is shown in theoperating sequence of FIG. 5. The heat pump may be operated according tothe method of FIG. 6 to ease transitions between heating and coolingmodes.

Referring to FIG. 1, a vehicle 10 including an engine 12, an electricalmachine 14, and an electrical energy storage device 11 is shown. In oneexample, the vehicle may be propelled solely via the engine 12, solelyvia the electrical machine 14, or by both the engine 12 and theelectrical machine 14. The electrical machine 14 may be suppliedelectrical power via the electrical energy storage device 11. Theelectrical energy storage device 11 may also be recharged via engine 12providing power to electrical machine 14 and electrical machineoutputting electrical energy to electric energy storage device 11.Alternatively, electrical energy storage device may be recharged viaconverting the vehicle's kinetic energy into electrical energy viaelectrical machine 14 during vehicle deceleration or hill descent.Electrical energy storage device 11 may also be recharged from astationary electrical power grid 17 via a home charging system or aremote charging system (e.g., a charging station) and electricalconductor 18. In one example, electrical energy storage device 11 is abattery. Alternatively, electrical energy storage device 11 may be acapacitor or other electric energy storage device.

Referring now to FIG. 2, a vehicle heating system or climate controlsystem 224 is shown. Devices and fluidic passages or conduits are shownas solid lines. Electrical connections are shown as dashed lines.

The vehicle 10 may include a driveline as shown in FIG. 3 or anothersuitable driveline to propel the vehicle 10 and/or power vehiclecomponents. Vehicle 10 is shown with internal combustion engine 12, andit may be selectively coupled to an electric machine (not shown).Internal combustion engine 12 may combust petrol, diesel, alcohol,hydrogen, or a combination of fuels.

The vehicle 10 may include a passenger compartment or cabin 220, anengine compartment 222, and a climate control system 224. The passengercompartment 220 may be within vehicle 10 and it may receive one or moreoccupants. A portion of climate control system 224 may be positioned inpassenger compartment 220.

Engine compartment 222 may be positioned proximate to passengercompartment 220. One or more power sources, such as internal combustionengine 12, as well as a portion of climate control system 224 may bewithin engine compartment 222. Engine compartment 222 may be isolatedfrom the passenger compartment 220 via bulkhead 226. The climate controlsystem 224 may circulate air and/or control or modify the temperature ofair that is circulated in the passenger compartment 220. Further, theinternal combustion engine 12 may be heated via climate control system224 to reduce fuel consumption and emissions. The climate control system224 may include a coolant subsystem 230, a heat pump subsystem 232, andventilation subsystem 234.

The coolant subsystem 230, which may also be referred to as a coolantloop, may circulate a coolant, such as glycol, to cool the internalcombustion engine 12. For example, waste heat that is generated by theinternal combustion engine 12 when the engine is running or operationalmay be transferred to the coolant and then circulated to radiator 231 tocool internal combustion engine 12. In at least one example, the coolantsubsystem 230 may include a coolant pump 240, a heater core 244, andintermediate heat exchanger 211 that may be fluidly interconnected byconduits or passages such as tubes, hoses, pipes, or the like. Thecoolant subsystem 230 includes radiator 231 for transferring thermalenergy to the ambient air surrounding the vehicle 10. The coolant pump240 may circulate coolant through the coolant subsystem 230. The coolantpump 240 may be powered by an electrical or non-electrical power source.For example, the coolant pump 240 may be operatively coupled to aninternal combustion engine 12 via a belt, or alternatively may be drivenby an electrically powered motor. The coolant pump 240 may receivecoolant from the internal combustion engine 12 and circulate the coolantin a closed loop. Specifically, when the climate control system 224 isin a heating mode, coolant may be routed from the coolant pump 240 tovalve 250 and intermediate heat exchanger 211, and then to the heatercore 244 before returning to the internal combustion engine 12 asrepresented by the arrowed lines. When internal combustion engine 12 isoutputting a higher level of thermal energy, coolant may flow from pump240 to radiator 231 before returning to internal combustion engine 12via heater core 244. Heater core heat sensor 237 provides heater coretemperature to controller 212.

The heater core 244 may transfer thermal energy from the coolant to airin the passenger compartment 220. The heater core 244 may be positionedin the passenger compartment 220 in the ventilation subsystem 234 andmay have any suitable configuration. For example, the heater core 244may have a plate-fin or tube-fin construction in one or more examples.

The heat pump subsystem 232 may operate in various modes, including, butnot limited to a cooling mode and heating mode. Further, heat pumpsubsystem may include a plurality of refrigerant circuits that may beisolated from other refrigerant circuits. For example, heat pumpsubsystem 232 includes a first refrigerant circuit that includes valve270, expansion valve 274, and interior heat exchanger 276. Heat pumpsubsystem includes a second refrigerant circuit that includes valve 270and bypass passage 285. In other variants, heat pump subsystem 232 mayinclude additional refrigerant circuits that provide additionalfunctionality. Thus, heat pump subsystem 232 may include a plurality ofrefrigerant circuits through which refrigerant passes.

In the cooling mode, the heat pump subsystem 232 may circulate a heattransfer fluid, which may be called a refrigerant, to transfer thermalenergy from inside the passenger compartment 220 to outside thepassenger compartment 220. Refrigerant may pass through interior heatexchangers 276 during cooling mode. In cooling mode, first control valve271 is in an open state such that first expansion valve 264 is bypassed.Second control valve 270 directs refrigerant to second expansion valve274, thereby preventing flow through bypass passage 285.

In a heating mode, the heat pump subsystem 232 may transfer thermalenergy from exterior heat exchanger 266 to intermediate heat exchanger211. Intermediate heat exchanger may be a gas to liquid heat exchangerwhich allows heat to be transferred to coolant, and the coolant may warmthe passenger cabin via heater core 244. In heating mode, first controlvalve 271 is closed such that first expansion valve 264 expandsrefrigerant that flows to exterior heat exchanger 266. Second controlvalve 270 directs refrigerant to bypass passage 285, thereby preventingflow through interior heat exchanger 276.

The pump 260, which may also be called a compressor, may pressurize andcirculate the refrigerant through the heat pump subsystem 232. The pump260 may be powered by an electrical or non-electrical power source. Forexample, the pump 260 may be operatively coupled to internal combustionengine 12 or driven by an electrically powered motor. The pump 260 mayprovide high pressure refrigerant to first expansion valve 264 andexterior heat exchanger 266 when first control valve 271 is closed.Refrigerant pressure may be determined via pressure sensor 241.Refrigerant may bypass expansion valve 264 when first control valve 271is in an open state. In some examples, an oil separator may be placed atthe outlet of pump 260. Refrigerant may flow through heat pump subsystem232 via motive force of compressor 260 in the direction of arrows 297.

The first expansion device 264 may be positioned between and may be influidic communication with pump 260 and the exterior heat exchanger 266.Temperature of exterior heat exchanger 266 may be sensed via temperaturesensor 239 and input to controller 212. The first expansion device 264may be provided to change the pressure of the refrigerant. For example,the first expansion device 264 may be a thermal expansion valve (TXV) ora fixed or variable position valve that may or may not be externallycontrolled. The first expansion device 264 may reduce the pressure ofthe refrigerant that passes through the first expansion device 264 fromthe pump 260 to the exterior heat exchanger 266. Therefore, highpressure refrigerant received from the pump 266 may exit the firstexpansion device 264 at a lower pressure and as a liquid and vapormixture in the heating mode.

The exterior heat exchanger 266 may be positioned outside the passengercompartment 220. In a cooling mode or air conditioning context, theexterior heat exchanger 266 may function as a condenser and may transferheat to the surrounding environment to condense the refrigerant from avapor to a liquid. In a heating mode, the exterior heat exchanger 266may function as an evaporator and may transfer heat from the surroundingenvironment to the refrigerant, thereby causing the refrigerant tovaporize.

The second control valve 270 may be positioned between external heatexchanger 266 and second expansion valve 274. The passage between secondcontrol valve 270 and second expansion valve 274 allows refrigerant toselectively reach internal heat exchanger 276. In one example, secondcontrol valve 270 is a three-way valve that selectively allowsrefrigerant to flow to second expansion valve 274 or bypass passage 285.

The accumulator 272 may act as a reservoir for storing any residualliquid refrigerant so that vapor refrigerant rather than liquidrefrigerant may be provided to the pump 260. The accumulator 272 mayinclude a desiccant that absorbs small amounts of water moisture fromthe refrigerant.

The interior heat exchanger 276 may be fluidly connected to the secondexpansion device 274. The interior heat exchanger 276 may be positionedinside the passenger compartment 220. In a cooling mode or airconditioning context, the interior heat exchanger 276 may function as anevaporator and may receive heat from air in the passenger compartment220 to vaporize the refrigerant. Refrigerant exiting the interior heatexchanger 276 may be routed to the accumulator 272. In the heating mode,interior heat exchanger 276 is bypassed.

The ventilation subsystem 234 may circulate air in the passengercompartment 220 of the vehicle 10. The ventilation subsystem 234 mayhave a housing 290, a blower 292, and a temperature door 294.

The housing 290 may receive components of the ventilation subsystem 234.In FIG. 2, the housing 290 is illustrated such that internal componentsare visible rather than hidden for clarity. In addition, airflow throughthe housing 290 and internal components is represented by the arrowedlines 277. The housing 290 may be at least partially positioned in thepassenger compartment 220. For example, the housing 290 or a portionthereof may be positioned under an instrument panel of the vehicle 10.The housing 290 may have an air intake portion 200 that may receive airfrom outside the vehicle 10 and/or air from inside the passengercompartment 220. For example, the air intake portion 200 may receiveambient air from outside the vehicle 10 via an intake passage, duct, oropening that may be located in any suitable location, such as proximatea cowl, wheel well, or other vehicle body panel. The air intake portion200 may also receive air only from or more than a predetermined amount(e.g., 75%) from inside the passenger compartment 220 and recirculatesuch air through the ventilation subsystem 234 (e.g. recirculationmode). One or more doors or louvers may be provided to permit or inhibitair recirculation.

The blower 292 may be positioned in the housing 290. The blower 292,which may also be called a blower fan, may be positioned near the airintake portion 200 and may be configured as a centrifugal fan that maycirculate air through the ventilation subsystem 234.

The temperature door 294 may be positioned between the interior heatexchanger 276 and the heater core 244. In the example shown, thetemperature door 294 is positioned downstream of the interior heatexchanger 276 and upstream of the heater core 244. The temperature door294 may block or permit airflow through the heater core 244 to helpcontrol the temperature of air in the passenger compartment 220. Forexample, the temperature door 294 may permit airflow through the heatercore 244 in the heating mode such that heat may be transferred from thecoolant to air passing through the heater core 244. This heated air maythen be provided to a plenum for distribution to ducts and vents oroutlets located in the passenger compartment 220. The temperature door294 may be moved between a plurality of positions to provide air havinga desired temperature. In FIG. 2, the temperature door 294 is shown in afull heat position in which airflow is directed through the heater core244.

Controller 212 includes executable instructions of the method in FIG. 6to operate the valves, fans, and pumps or compressors of the systemshown in FIG. 2. Controller 212 includes inputs 201 and outputs 202 tointerface with devices in the system of FIG. 2. Controller 212 alsoincludes a central processing unit 205 and non-transitory memory 206 forexecuting the method of FIG. 6.

It should be noted that in some example systems, engine 12 and heatercore 244 may not be present. In such systems, interior heat exchanger276 may operate as a condenser in a heating mode and exterior heatexchanger 266 may operate as an evaporator. Consequently, in the methodof FIG. 6 and the block diagram of FIG. 4, internal heat exchanger 276may be substituted for heater core 244.

Referring now to FIG. 3, a block diagram of a vehicle driveline 300 invehicle 10 is shown. Driveline 300 may be powered by engine 12. Engine12 may be started with an engine starting system including starter 301or via electric machine or driveline integrated starter generator (DISG)14. Further, engine 12 may generate or adjust torque via torque actuator309, such as a fuel injector, throttle, camshaft, etc.

An engine output torque may be transmitted to driveline disconnectclutch 304. Driveline disconnect clutch selectively couples anddecouples driveline 300. Driveline disconnect clutch 304 may beelectrically or hydraulically actuated. The downstream side of drivelinedisconnect clutch 304 is shown mechanically coupled to DISG input shaft303.

DISG 14 may be operated to provide torque to driveline 300 or to convertdriveline torque into electrical energy to be stored in electric energystorage device 11. DISG 14 has a power output that is greater thanstarter 301. Further, DISG 14 directly drives driveline 300 or isdirectly driven by driveline 300. There are no belts, gears, or chainsto couple DISG 14 to driveline 300. Rather, DISG 14 rotates at the samerate as driveline 300 and may be mechanically coupled to transmission308 via shaft 336. Electrical energy storage device 11 may be a battery,capacitor, or inductor. The downstream side of DISG 14 is mechanicallycoupled to transmission 308.

Automatic transmission 308 includes gear clutches 333 (e.g., gears 1-6)for adjusting a transmission gear ratio. The gear clutches 333 may beselectively engaged to propel vehicle 10. Torque output from theautomatic transmission 308 may in turn be relayed to wheels 316 topropel the vehicle via output shaft 334. Output shaft 334 deliverstorque from transmission 308 to wheels 316. Automatic transmission 308may transfer an input driving torque to the wheels 316.

Further, a frictional force may be applied to wheels 316 by engagingwheel friction brakes 318. In one example, wheel friction brakes 318 maybe engaged in response to the driver pressing his foot on a brake pedal(not shown). In other examples, controller 212 or a controller linked tocontroller 212 may engage wheel friction brakes. In the same way, africtional force may be reduced to wheels 316 by disengaging wheelfriction brakes 318 in response to the driver releasing his foot from abrake pedal. Further, vehicle brakes may apply a frictional force towheels 316 via controller 212 as part of an automated engine stoppingprocedure.

Controller 212 may be programmed to receive inputs from engine 12 andaccordingly control a torque output of the engine and/or operation ofthe torque converter, transmission, DISG, clutches, and/or brakes. Asone example, an engine torque output may be controlled by adjusting acombination of spark timing, fuel pulse width, fuel pulse timing, and/orair charge, by controlling throttle opening and/or valve timing, valvelift and boost for turbo- or super-charged engines. In all cases, enginecontrol may be performed on a cylinder-by-cylinder basis to control theengine torque output. Controller 212 may also control torque output andelectrical energy production from DISG by adjusting current flowing toand from DISG windings as is known in the art. Controller 212 may alsoinclude non-transitory memory for storing executable instructions of themethod described in FIG. 6.

Thus, the system of FIGS. 1-3 provides for a vehicle system, comprising:a heat pump system; and a controller including executable instructionsstored in non-transitory memory for providing a bumpless (e.g., nochange in the command) compressor command between a transition betweentwo different heat pump operating modes. The vehicle system includeswhere the bumpless compressor command is a command that remains at asame value when the heat pump system is transitioned between the twodifferent heat pump operating modes. The vehicle system furthercomprises adjusting the compressor command in response to an amount oftime since the transition between the two different heat pump operatingmodes. The vehicle system includes where a first mode of the twodifferent modes is a heating mode and where a second mode of the twodifferent modes is a cooling mode. The vehicle system further comprisesadditional executable instructions for switching the heat pump systembetween the two different heat pump operating modes. In some examples,the vehicle system further comprises additional executable instructionsfor providing the bumpless compressor command based on output values oftwo different PID controllers.

Referring now to FIG. 4, a block diagram of an example heat pumpcontroller is shown. Instructions for a controller as described in FIG.4 may be included in the system of FIGS. 1-3 as executable instructionsstored in non-transitory memory. Further, the controller illustrated inFIG. 4 along with the method of FIG. 6 may provide the sequence shown inFIG. 5.

Desired evaporator temperature for a cooling mode of an example heatpump as shown in FIG. 2 enters controller 400 at 402. The desiredevaporator temperature may be stored in memory based on user (passenger)or controller input. Actual evaporator temperature enters controller 400at 404. The actual evaporator temperature may be a temperature of finsof evaporator 276 as is shown in FIG. 2. The actual evaporatortemperature may be determined via a temperature sensor. The actualevaporator temperature is subtracted from the desired evaporatortemperature at summing junction 414 which outputs an evaporatortemperature error. The evaporator temperature error is input intoproportional/integral/derivative (PID) controller 420 which operates asan evaporator temperature controller. The evaporator temperature erroris operated on by proportional, integral, and derivative gains. The PIDcontroller sums proportional, integral, and derivative terms andsupplies the result to summing junction 430.

Desired refrigerant pressure for the heat pump shown in FIG. 2 enterscontroller 400 at 406. The desired refrigerant pressure may beempirically determined and stored in memory. Actual refrigerant pressureenters controller 400 at 408. The actual refrigerant pressure may bedetermined via a pressure sensor as is shown in FIG. 2. The actualrefrigerant pressure is subtracted from the desired refrigerant pressureat summing junction 416 which outputs a refrigerant pressure error. Therefrigerant pressure error is input intoproportional/integral/derivative (PID) controller 422 which operates asa refrigerant pressure controller. The refrigerant pressure error isoperated on (e.g., multiplied) by proportional, integral, and derivativegains. The PID controller sums proportional, integral, and derivativeterms and supplies the result to summing junctions 430 and 432.

Desired heater core temperature for the heat pump system shown in FIG. 2enters controller 400 at 410. The desired heater core temperature may beempirically determined and stored in memory. Actual heater coretemperature enters controller 400 at 412. The actual heater coretemperature may be determined via a temperature sensor as is shown inFIG. 2. The actual heater core temperature is subtracted from thedesired heater core temperature at summing junction 418 which outputs aheater core temperature error. The heater core temperature error isinput into proportional/integral/derivative (PID) controller 424 whichoperates as a heater core temperature controller. The heater coretemperature error is operated on (e.g., multiplied) by proportional,integral, and derivative gains. The PID controller sums proportional,integral, and derivative terms and supplies the result to summingjunction 432.

The output of summing junction 430 is directed to summing junction 434and bumpless transfer algorithm 444. Bumpless transfer algorithm 444also provides input to summing junction 434, and output of summingjunction 434 is supplied to switch 450. Similarly, output of summingjunction 432 is directed to summing junction 436 and bumpless transferalgorithm 444. Bumpless transfer algorithm 444 provides output tosumming junction 436, and output of summing junction 436 is supplied toswitch 450.

Mode switching system 440 includes logic for determining when to switchbetween heat pump operating modes such as heating mode and cooling mode.Mode switching system 440 may choose to switch from heating mode tocooling mode or vice-versa in response to a driver's request, ambientand passenger cabin conditions, or in response to an automated climatecontrol request. For example, if a driver wishes to increase passengercabin temperature to a greater temperature than ambient temperature,mode switching system 440 may transitions the heat pump from coolingmode to heating mode. Further, mode switching system 440 may transitionthe heat pump from cooling mode to heating mode in response to a driverspecifically requesting a change from cooling mode to heating mode via aclimate control system interface.

Bumpless transfer algorithm 444, as described in further detail in FIG.6, adjusts integral gains for the evaporator temperature PID controller,the refrigerant pressure PID controller, and the heater core temperaturePID controller. The bumpless transfer algorithm also determines feedforward terms based on a difference output of the evaporator temperaturePID controller and the heater core temperature PID controller. The feedforward evaporator temperature command is output to summing junction434. The feed forward heater core temperature command is output tosumming junction 436. Summing junction 434 provides the evaporatortemperature command to switch 450, and summing junction 436 provides theheater core temperature command to switch 450.

Switch 450 provides either the evaporator temperature command or theheater core temperature command to the compressor, the other of which isnot used to control the compressor. Compressor speed is controlled bythe output of switch 450. Switch 450 is operated by input from modeswitching system 440. If mode switching system 440 selects cooling mode,the evaporator temperature command is supplied to compressor 452 byswitch 450. If mode switching system 440 selects heating mode, theheater core temperature command is supplied to compressor 452 by switch450.

Thus, controller 400 supplies control commands to compressor 452 basedon a desired evaporator temperature and a desired refrigerant pressurein a cooling mode. Controller 400 also provides control commands tocompressor 452 based on a desired heater core temperature and thedesired refrigerant pressure in heating mode. Feed forward terms orcontrol commands in heating and cooling modes are based on a differencein evaporator PID controller output and heater core PID controlleroutput. The feed forward terms exponentially decay as a time since amode switch increases as is shown in the sequence of FIG. 5. Thecommands are supplied to the compressor to provide a desired evaporatortemperature or a desired heater core temperature.

Referring now to FIG. 5, a simulated sequence for operating a vehicleheat pump according to the method of FIG. 6 is shown. The sequence maybe performed by the system shown in FIGS. 1-3.

The first plot from the top of FIG. 5 is a plot of heat pump mode versustime. The Y axis represents heat pump mode and the heat pump is in aheating mode when the trace is near the Y axis arrow. The heat pump isin a cooling mode when the trace is near the X axis. The X axisrepresents time and time increases from the left side of FIG. 5 to theright side of FIG. 5.

The second plot from the top of FIG. 5 is a plot of heating mode andcooling mode compressor commands versus time. The solid line 502represents the cooling compressor command (e.g., output of summingjunction 434 of FIG. 4). The dashed line 504 represents the heatingcompressor command (e.g., output of summing junction 436 of FIG. 4). TheY axis represents heating or cooling compressor command and heating andcooling commands increase in magnitude in the direction of the Y axisarrow. The X axis represents time and time increases from the left sideof FIG. 5 to the right side of FIG. 5.

The third plot from the top of FIG. 5 is a plot of feed forward coolingcommand (e.g., output of bumpless transfer algorithm 444 that enterssumming junction 434) versus time. The X axis represents time and timeincreases from the left side of FIG. 5 to the right side of FIG. 5.

The fourth plot from the top of FIG. 5 is a plot of feed forward heatingcommand (e.g., output of bumpless transfer algorithm 444 that enterssumming junction 436) versus time. The X axis represents time and timeincreases from the left side of FIG. 5 to the right side of FIG. 5.

The fifth plot from the top of FIG. 5 is a plot of the compressorcommand versus time. The magnitude of the compressor command increasesin the direction of the Y axis arrow. The X axis represents time andtime increases from the left side of FIG. 5 to the right side of FIG. 5.The compressor command is based on the cooling command and the heatingcommand.

At time T0, the heat pump is in heating mode and the heating command isat a lower middle level. The cooling command is at a higher level basedon a compressor speed to drive the actual evaporator temperature to adesired evaporator temperature. The feed forward cooling and heatingcommands are zero since a significant amount of time has elapsed sincethe mode change into heating mode. The compressor command is at a lowermiddle level since it is based on the heating command.

At time T1, the heat pump operating mode is changed from heating mode tocooling mode as indicated by the mode trace. The mode may change inresponse to driver input or in response to ambient and passenger cabinenvironmental conditions. The cooling command is a combination of anexponential feed forward term and the evaporator temperature PID controlterm, as such, it decreases to a same level as the heating command andit begins to increase exponentially to a higher level. The heatingcommand output decreases in response to the heater core temperature. Thefeed forward cooling command, which the cooling command is based from,increases to a level based on a difference between the heating commandand the cooling command. The feed forward cooling command then decreasesexponentially in response to time since the mode change increasing. Bydecreasing the feed forward command, the compressor command starts at acommand that is equivalent to the compressor command before the modechange. Thus, the compressor command provides a bumpless change incontrol between the heating and cooling modes. The compressor command isa combination of an exponential feed forward term and the heater coretemperature PID control term, as such, it increases exponentially to anew constant value after a predetermined amount of time expires. Thefeed forward heating command remains at a value of zero.

At time T2, the heat pump operating mode is changed back from coolingmode to heating mode as indicated by the mode trace. The mode may changein response to driver input or in response to ambient and passengercabin environmental conditions. The cooling command decreasesexponentially by a small amount and levels off at a constant lowervalue; however, the cooling command may not decrease exponentially or bya small amount. The heating command output increases in a step like wayand then it begins to decrease exponentially since it is formed from theexponential feed forward term and the PID controller output. The heatingcommand is increased to a level of the cooling command at the time ofthe mode transition so that compressor speed does not change stepwise inresponse to the mode change. The feed forward cooling command remains ata value of zero and the feed forward heating command increases and thendecreases exponentially. The compressor command is held at a constantvalue at the time of the mode transition and then it decays or isreduced exponentially after the mode changes from heating mode tocooling mode.

In this way, commands of two different modes may be a basis for acompressor command that does not change in an impulse or stepwise mannerin response to a change from a heat pump transitioning from a heatingmode to a cooling mode or vice-versa. Rather, the compressor command ismaintained at a level during a heat pump mode change and then itincreases or decreases exponentially to provide the desired heat pumpoutput.

Referring now to FIG. 6, a method for operating a heat pump is shown.The method of FIG. 6 may be applied to the system of FIGS. 1-3. Further,the method of FIG. 6 may provide the operating sequence of FIG. 5.Additionally, the method of FIG. 6 may be stored as executableinstructions in non-transitory memory of a controller.

At 602, method 600 determines a heat pump operating mode. The heat pumpoperating mode may be determined in response to driver or passengerinputs to a climate control system. For example, a driver may requestheating mode by selecting heat on a climate control panel.Alternatively, method 600 may select the heat pump operating mode basedon ambient environmental conditions and passenger cabin conditions. Forexample, method 600 may change the heat pump from cooling mode toheating mode when ambient temperature is less than a desired cabintemperature. Method 600 proceeds to 604 after the heat pump operatingmode is selected.

At 604, method 600 judges if a heat pump mode change is requested.Method 600 may judge that a heat pump mode change is requested inresponse to a bit in memory changing state, and the bit may change statefrom a value of one in heating mode to a value of zero in cooling mode.If method 600 judges that a mode change is requested, the answer is yesand method 600 proceeds to 606. Otherwise, the answer is no and method600 proceeds to 612.

At 606, method 600 resets a timer that accumulates time since atransition from one heat pump operating mode to a second heat pumpoperating mode. For example, the timer accumulates time since the heatpump changes from heating mode to cooling mode or vice-versa. Method 600begins to perform operations to provide a bumpless command transferbetween heating and cooling modes or vice-versa at steps 606 to 610.Bumpless transfer is an operation that provides a same compressorcommand after a heat pump mode change as before the heat pump modechange. The compressor command may change as time since the mode changeincreases, but it is held constant during the actual heat pump modechange. By maintaining the compressor command during a heat pump modechange, it is possible to change heat pump operating modes withoutcausing a significant change in the compressor command even though thesystem changes from a heating mode to a cooling mode. Method 600proceeds to 608 after the timer is reset.

At 608, method 600 resets appropriate PID integrators and it determinesa difference between PID controller commands. For example, if the heatpump mode change is from a heating mode to a cooling mode, method 600resets to zero the integrators of the refrigerant pressure control PIDcontroller (e.g., PID controller 2 of FIG. 4) and the heater coretemperature PID controller (e.g., PID controller 3 of FIG. 4). Method600 also determines a difference in the output of a heating commandbased on desired heater core temperature (e.g., output of summingjunction 430 of FIG. 4) and a cooling command based on desiredevaporator temperature (e.g., output of summing junction 432 of FIG. 4).In particular, method 600 subtracts the cooling command value from theheating command value to determine a PID controller output difference.

On the other hand, if method 600 changes the heat pump operating modefrom cooling mode to heating mode, method 600 resets to zero theintegrators of the refrigerant PID controller (e.g., PID controller 2 ofFIG. 4) and the evaporator temperature PID controller (e.g., PIDcontroller 1 of FIG. 4). Method 600 also determines a difference in theoutput of a heating command based on desired heater core temperature(e.g., output of summing junction 430 of FIG. 4) and a cooling commandbased on desired evaporator temperature (e.g., output of summingjunction 432 of FIG. 4). In particular, method 600 subtracts the heatingcommand value from the cooling command value to determine a PIDcontroller output difference. Method 600 proceeds to 610 after theappropriate integrators are reset and the difference between heating andcooling commands is determined.

At 610, method 600 determines new feed forward cooling or heating modeterms or command values and integrator gain values responsive to theheat pump mode change request. If the heat pump mode changes fromheating to cooling, method 600 determines the cooling feed forwardcommand which is the value e to the power of a predetermined constant−Ke1 multiplied by time, and the result is multiplied by the coolingcommand value minus the heating command value (e.g.,Cooling_FF=(PID_EVAP−PID_HCT)*exp(−Ke1*time) where Cooling_FF is thefeed forward cooling command, PID_EVAP is output of summing junction430, PID_HCT is output of summing junction 432, time is the amount oftime since the heat pump mode transition, exp represents the constant e(e.g., 2.718), and Ke1 is a predetermined gain). The evaporator PIDcontroller integrator gain is Integral_Gain1=Ki1*(1−exp(−Ke1*time)),where Integral_Gain1 is the evaporator integrator gain, Ki1 is apredetermined integrator gain, exp is the constant e, time is the amountof time since the heat pump mode transition. The refrigerant integratorgain is given by Integral_Gain2=Ki2*(1−exp(−Ke1*time)), where Ki2 is apredetermined gain and the remaining terms are as described previously.

If the heat pump mode changes from cooling to heating, method 600determines the heating feed forward command which is the value e to thepower or a predetermined constant −Ke2 multiplied by time, multiplied bythe heating command value minus the cooling command value (e.g.,Heating_FF=(PID_HCT−PID_EVAP)*exp(−Ke2*time) where Heating_FF is thefeed forward heating command, PID_EVAP is output of summing junction430, PID_HCT is output of summing junction 432, time is the amount oftime since the heat pump mode transition, and Ke2 is a predeterminedgain). The heater core temperature PID controller integrator gain isIntegral_Gain3=Ki3*(1−exp(−Ke2*time)), where Integral_Gain3 is theheater core temperature integrator gain, Ki3 is a predetermined gain,Ki2 is a predetermined integrator gain, exp is the value e, time is theamount of time since the heat pump mode transition. The refrigerantintegrator gain is given by Integral_Gain2=Ki2*(1−exp(−Ke2*time)), wherethe terms are as described previously. Method 600 proceeds to 612 afterintegrator gains and feed forward values are determined.

At 612, method 600 judges if method 600 is in a heating mode. In oneexample, method 600 judges that the heat pump is in a heating mode basedon a value of a bit stored in memory. For example, if the bit has avalue of one, the answer is yes and method 600 proceeds to 618.Otherwise, the answer is no and method 600 proceeds to 614.

At 618, method 600 provides a heater core temperature error to a heatercore temperature PID controller (e.g., 424 of FIG. 4). Method 600provides refrigerant pressure error to a refrigerant pressure PIDcontroller (e.g., 422 of FIG. 4). Method 600 also adds the output of theheater core temperature PID controller and the refrigerant pressure PIDcontroller as shown at 432 of FIG. 4. Method 600 proceeds to 620 afterthe PID controller outputs are added together.

At 620, method 600 adds the sum of the refrigerant pressure PIDcontroller and the heater core temperature PID controller to the heatingmode feed forward command determined at 610 as shown at 436 of FIG. 4.The heating mode feed forward command is output from the bumplesstransfer algorithm described at 606 to 610.

At 622, method 600 outputs the compressor command. The compressorcommand may be the sum of the refrigerant pressure PID controlleroutput, the heater core temperature PID controller output, and theheating mode feed forward command determined at 610 if the heat pump isin heating mode. Alternatively, the compressor command may be the sum ofthe refrigerant pressure PID controller output, the evaporatortemperature PID controller output, and the cooling mode feed forwardcommand determined at 610 if the heat pump is in cooling mode. Thecompressor command operates on the compressor to increase, decrease, ormaintain compressor speed.

At 614, method 600 provides an evaporator temperature error to anevaporator temperature PID controller (e.g., 420 of FIG. 4). Method 600provides refrigerant pressure error to a refrigerant pressure PIDcontroller (e.g., 422 of FIG. 4). Method 600 also adds the output of theevaporator temperature PID controller and the refrigerant pressure PIDcontroller as shown at 430 of FIG. 4. Method 600 proceeds to 616 afterthe PID controller outputs are added together.

At 616, method 600 adds the sum of the refrigerant pressure PIDcontroller and the evaporator temperature PID controller to the coolingmode feed forward command determined at 610 as shown at 434 of FIG. 4.The cooling mode feed forward command is output from the bumplesstransfer algorithm described at 606 to 610.

Thus, a heat pump compressor command may be held to a constant valueduring a heat pump mode change so that the heat pump compressor speed isnot needlessly moved between control values during a heat pump modechange. The heat pump compressor command may change as time increasesfrom a time of the mode change so that the compressor command convergesto a command that provides a desired evaporator temperature or a desiredheater core temperature. By eliminating or reducing heat pump compressorcommand changes during heat pump mode changes, it may be possible toextend compressor life and reduce the possibility of heat pumpdegradation.

The method of FIG. 6 may provide for a heat pump method, comprising:commanding a compressor to provide a desired evaporator temperature inresponse to output of an evaporator temperature controller and output ofa refrigerant pressure controller in a first heat pump operating mode;and commanding the compressor to provide a desired heater coretemperature in response to output of a heater core temperaturecontroller and output of the refrigerant pressure controller in a secondheat pump operating mode. The method includes where the first heat pumpoperating mode is a cooling mode, and where the second heat pump mode isa heating mode. The method further comprises adding a cooling feedforward command to the output of the evaporator temperature controllerin the first heat pump operating mode. The method further comprisesadding a heating feed forward command to the output of the heater coretemperature controller in the second heat pump operating mode.

In some examples, the method further comprises adjusting integratorgains in response to transitioning from the first heat pump operatingmode to the second heat pump operating mode. The method furthercomprises resetting an integrator output to zero in response totransitioning from the first heat pump operating mode to the second heatpump operating mode. The method further comprises switching commandingthe compressor to provide the desired evaporator temperature tocommanding the compressor to provide the desired heater core temperaturein response to a request to change a heat pump operating mode.

The method of FIG. 6 also provides for a heat pump method, comprising:providing a compressor command via adjusting a sum of a firstproportional/integral/derivative (PID) controller output and a secondPID controller output based on a difference between the sum of the firstPID controller output and the second PID controller output and a sum ofa third PID controller output and the second PID controller output; andoperating a compressor in response to the compressor command. The methodincludes where the first PID controller outputs a command based onevaporator temperature, where the second PID controller outputs acommand based on refrigerant pressure, and where the third PIDcontroller outputs a command based on heater core temperature.

In some examples, the method further comprises adjusting the sum of thefirst PID controller and the second PID controller based on a decayingexponential time based term. The method further comprises zeroingintegrators of the second PID controller and the third PID controller inresponse to transitioning to a heat pump cooling mode where thecompressor command is provided. The method further comprises adjustingintegral gains of the first PID controller and the second PID controllerin response to transitioning to the heat pump cooling mode. The methodalso further comprises providing the compressor command via adjusting asum of the third PID controller output and the second PID controlleroutput based on a heating feed forward command. The method furthercomprises providing the compressor command via multiplying the sum ofthe third PID controller output and the second PID controller output bya decaying exponential term.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller

This concludes the description. The reading of it by those skilled inthe art would bring to mind many alterations and modifications withoutdeparting from the spirit and the scope of the description.

The invention claimed is:
 1. A vehicle system, comprising: a heat pumpsystem; and a controller including executable instructions stored innon-transitory memory for providing a compressor command for a bumplesstransfer between a transition between two different heat pump operatingmodes and adjusting the compressor command in response to an amount oftime since the transition between the two different heat pump operatingmodes.
 2. The vehicle system of claim 1, where the compressor command isa command that remains at a same value during the transition between thetwo different heat pump operating modes.
 3. The vehicle system of claim1, where a first mode of the two different modes is a heating mode andwhere a second mode of the two different modes is a cooling mode.
 4. Thevehicle system of claim 1, further comprising additional executableinstructions for switching the heat pump system between the twodifferent heat pump operating modes.
 5. The vehicle system of claim 1,further comprising additional executable instructions for providing thecompressor command for the bumpless transition based on output values oftwo different PID controllers.
 6. The vehicle system of claim 5, whereinthe output values of the two different PID controllers are summed. 7.The vehicle system of claim 1, further comprising additional executableinstructions for providing the compressor command for the bumplesstransition based on output values of three different PID controllers. 8.The vehicle system of claim 7, wherein the output values are a first sumof first and second PID controllers and a second sum of second and thirdPID controllers.
 9. The vehicle system of claim 7, wherein one or moreoutput values are adjusted based on a decaying exponential time basedterm.
 10. The vehicle system of claim 1, wherein the compressor commandis based on outputs of two or more PID controllers.
 11. The vehiclesystem of claim 10, comprising additional executable instructions foradjusting gains of at least one of the two or more PID controllers inresponse to the transition between the two different heat pump operatingmodes.